The present invention pertains in general to probes for cavity resonators and in particular to combiner probes having compensation for a discontinuity capacitance.
In recent years the dominant approach for power combining has been the use of a cylindrical cavity coupled to several microwave semiconductor devices. In this approach, as the number of diodes in a combiner increases, the output coupling coefficient, .beta..sub.2N, has to increase according to a well established set of design equations as discussed in "Efficient Power Combining," by M. Dydyk, appearing in IEEE Transactions on Microwave Theory and Technique, July 1980, at pages 755-762. Specifically, the relationship for the coupling coefficient, .beta..sub.2N, of a diode combiner having N diodes to the coupling coefficient, .beta..sub.21.sbsb.ideal, for a single diode combiner is given by: EQU .beta..sub.2N =N(1+.beta..sub.21.sbsb.ideal)-1 (1)
In order to achieve tight coupling with more than one diode, M. Dydyk proposed a transformer in a probe assembly in his U.S. Pat. No. 4,340,870. However, for existing probes, the ability to couple to a cavity is accompanied by a limitation on maximum output coupling coefficients and a frequency detuning of the cavity resonant frequency due to a discontinuity capacitance at the probe site. Furthermore, this discontinuity capacitance can greatly reduce the effect of a transformer in the probe assembly.
In order to be able to achieve any desired coupling for efficient, multiple diode oscillators, the discontinuity capacitance at the probe site must be eliminated. The frequency shift due to such a discontinuity capacitance can be circumvented by using a cavity tuning screw, but in multiple cavity oscillators this is a tedious and inaccurate operation.